Apparatus for mixing concrete and the like



July 27, 1937. w. M. VENABLE APPARATUS FOR MIXING CONCRETE AND THE LIKEFiled Feb. 11, 1956 5 Sheets-Sheet 1 INVENTOR 414684. Wa dww e/al I July27, 1937. w. M. VENABLE APPARATUS FOR MIXING CONCRETE AND THE LIKE FiledFeb. 11, 1936 5 Sheets-Sheet 2 INVENTOR July 27, .1937. w. M. VENABLE I2,088,099

' APPARATUS FOR MIXING CQNCRETE AND THE LIKE Filed Feb. i1. 193a 3Sheets-Sheet 5 INVENTOR Patented July 27, 1937 APPARATUS FOR MKXHNGCONCRETE AND THE LIKE William Mayo Venable, Pittsburgh, Pa, assignor toBlaw-Knox Company, Elawnox, Pa., a C01? poration of New JerseyApplication February 11, 1936, Serial No. 63,371

'7 Claims. (Cl. 83-73) This invention relates generally to a method andapparatus for mixing concrete and the like and more particularly totruck mixers in which the mixing operation is carried out during thetransit of the mixer. In this type of mixer particularly, it isimportant that it be capable of taking as large a charge as possible fora given three-fourths full with unmixed materials which} when mixed,occupy about two-thirds of the drum capacity. The present inventionrelates particularly to the shape and arrangement of the mixing vanes,whereby a very effective mix-V ing action is obtained, the other partsof the apparatus being conventional.

In accordance with the preferred embodiment of the present invention, acylindrical mixing drum is employed. It is provided with mixing vaneswhich are secured to the inside of the drum in such manner that thelines of juncture of the vanes with the drum form an interrupted helix.The ends of the vanes at their proximal edges, that is, the edges whichare secured to the drum, are spaced apart so as to provide spaces forportions of the water and concrete to pass therethrough rather thanbeing picked up and carried on the vanes. The ends of adjacent vanes attheir distal edges, that is, the edges farthest away from the line ofjuncture of the vanes with the drum, are secured to each other as bywelding in order to provide a rigid structure of vanes. The distal edgesof the vanes thus form a continuous though imperfect helix. The faces ofthe vanes are curved or bent so as to make them trough-shaped in orderthat they may be capable of picking up those portions of the batch whichlie adjacent the drum surface, raising such portions above the mainlevel of the batch and then discharging the portions into the batch atpoints displaced axially of the drum. The greater part of the concreteis not picked up by the vanes, but rolls or tumbles from one side of thedrum to the other, very similar to the action which would take place ifan ordinary barrel were filled two-thirds full of material and rolled onits side. The main portion of the batch which rolls upon itself ismaintained in relatively the same position longitudinally of the drum.The small portions which are picked up by the vanes are raised above themain level of the batch and there discharged upon the batch at pointswhich are spaced longitudinally of the drum with respect to the placesat which such small portions were picked up by the vanes. This causesthe concrete to pile up slightly toward the discharge end of the drumwhich is provided with a cover which may be removed during thedischarging operation. Each of the vanes, in addition to beingtrough-shaped so as to enable it to retain and raise a small portion ofthe batch above the main batch of concrete, is secured to the drum sothat when it is in its uppermost position its edges are inclineddownwardly longitudinally of the drum at an angle to the drum axis whichis approximately'the angle of repose of the concrete when the vane is inits uppermost position. In other Words, the line of juncture of eachvane with the drum, and the distal edge of each vane, each forms anangle with the axis of the drum when the vane is in its uppermostposition, which approximately equals the angle of repose of theconcrete. This angle is approximately 45, al-

though it Will vary in either direction 10 or 15 degrees according tothe consistency and com position of the concrete.

Due to the use of trough-shaped mixing vanes and also because of theirarrangement in the drum in the form of an interrupted or broken helix,it is unnecessary to reverse the direction of rotation of the drum atintervals in order to obtain the proper mixing action. In the presentinvention, efiicient mixing may be obtained by rotating the drum in onedirection only so as to cause the concrete to be crowded toward thedischarge end of the drum. This is a distinct advantage over thosemixers which depend for efiicient mixing on periodically reversing therotation of the drum. One such mixer which requires the reversing of thedrum is described in McCrery Patent No. 1,999,843, granted April 30,1935, and assigned to the assignee of the present application. In theMcCrery patent, because of the use of mixing vanes having fiat faces,the drum must be reversed during mixing and the mixing action is notsuificiently effective if it is attempted to use it with a batch whichmore than half fills the drum. The vanes of the Mo- Crery patent beingflat, are not capable of raising small portions of the concrete abovethe main level of the batch and then discharging them again into themain batch at points which are displaced longitudinally of the drum fromthe points where such portions were picked up. The elimination ofreversing mechanism for the drum and the fact that the drum may becharged more fully and still obtain efiicient mixing action areimportant advantages of the present invention.

In the accompanying drawings which illustrate two embodiments of myinvention,

Figure l is, in part, a side elevation and, in part, a longitudinalvertical section through the mixing drum;

Figure 2 is a transverse vertical section through the drum on the lineII-II of Figure 1;

Figure 3 is a view similar to Figure 1 illustrating the drum with abatch therein and showing the action of the mixing vanes;

Figure 4 is a perspective view showing a portion of the mixing drum andcertain of the mixing vanes, illustrating the spaces between theproximal edges of adjacent vanes;

Figure 5 is a front elevation of one of the vanes;

Figure 6 is an enlarged transverse vertical section of a vane taken onthe line VI-VI of Figure 4 and showing a small section of the drum;

Figure '7 is a view similar to Figure 1, but showing a modifiedarrangement of vanes in which the proximal edges of the vanes form acontinuous though imperfect helix and in which the distal edges of thevanes are spaced apart; and

Figure 8 is a transverse vertical section through the drum of Figure '7taken on the line VIIIVIII of Figure '7.

Referring now more particularly to the accompanying drawings and for thepresent to the embodiment shown in Figures 1 through 6, there is shown amixing drum 2 of conventional form having a cylindrical body portion 3,conical end portions i, a charging opening 6 provided with a cover I anda discharge opening 8 provided with a cover 9. The forward end of thedrum is closed by a plate 3a. The drum is provided with means forsupporting and rotating it, but such means are not shown since they maybe of any suitable kind.

Secured to the inside; of the drum as by welding is a plurality ofmixing vanes l5, ll, l2 and I3. These vanes are so arranged as to forman interrupted helix around the drum at the lines of juncture of thevanes with the drum. In the embodiment shown, four of these vanes extendapproximately half way around the drum, although a greater or lessernumber of vanes may be employed. Also, the number of helixes employed inthe drum may be varied. It is preferred, however, to employ two of thesehelixes, each helix extending half way around the drum. One of the vanesis illustrated in Figure 5. It is bent or curved about its longitudinalaxis ab sothat it is trough-shaped in order that it may maintain a smallportion of concrete on its surface until the vane is raised to itsuppermost position, whereupon this small portion is discharged into themain batch of concrete which has not been lifted by the vanes. The face[5 of the vane l0 illustrated in Figure 5 is concave. The curvature ofthe vanes is best illustrated in Figure 6 which is an enlarged verticaltransverse section through the vane l2 of Figure 4. The vane I2 issecured to the drum by welding as indicated by the reference numeral 16in Figure 6. The vane is preferably curved so that the plane 0 which istangent to the curvature of the vane at its distal edge ll makes anangle at of approximately 45 with the vertical plane 6 through thedistal edge of the vane.

The proximal edges I8 of the vanes are secured to the inside of the drumby welding 15. The ad jacent ends of the vanes at their proximal edgesare spaced from each other, but at their distal edges are welded to eachother in order to form a strong structure of vanes. Thus, as shown inFigure 4, the proximal edges iii of vanes i2 and 3 at their adjacentends E20. and 53a are spaced from each other so as to form a space 1which is generally triangular in shape, but having curved sides, thebottom side being formed by the curved surface of the drum 2 and theother two sides being formed by the adjacent ends Ma and l3a of the twovanes l2 and 33. This space J allows water to flow therethrough ratherthan being picked up by the vanes, thereby giving more efficient mixing.The adjacent ends 22a and Ma of the vanes 52 and 53 are welded to--gether at their distal edges I! as indicated by the reference numerall9, as are also the other vanes. of the vanes with the drum are notcontinuous, but are interrupted so that the vanes at their proximaledges formv an interrupted helix rather than a true helix. The distaledges of adjacent vanes meet at the adjacent corners and are weldedtogether so as to form a continuous though imperfect helix.

In carrying out the mixing of a batch of concrete, the drum is filledabout three-fourths full and is rotated in a clockwise direction asindicated by the arrow in Figure 2. The greater part of the batch simplyrolls or tumbles over upon itself, but small portions of the concretewhich lie adjacent the surface of the drum in the path of the vanes arepicked up by the vanes, raised above the main batch and thereafter againdischarged into the batch at points displaced longitudinally from thepoints at which they were picked up. In Figures 1 and 3, the vane I9 isshown in its uppermost position. In rising from its lowermost to itsuppermost position, the vane IQ, for example, picks up a small portionof concrete, raises it above the surface indicated by the line 20 of themain batch shown in Figure 3 and discharges it again into the batch at apoint nearer the discharge end of the drum than the point from which theportion was raised from the batch. The portion being discharged from thevane I53 is indicated in Figure 3 by the reference numeral 9. Each ofthe vanes acts in a similar manner to raise a small portion of theconcrete above the main level of the batch and dump it onto the batchnearer the discharge end of the drum than the point from which it waspicked up. While this raising of the small portions above the main levelof the batch and dumping it again onto the batch is taking place, themain portion of the batch simply rolls or tumbles on itself. There isthus provided a combined mixing action which is very eflective. Theeffect of raising small portions of the batch above the main level andagain dumping them onto the batch is to raise the level of the concretetoward the discharge end of the drum, as is shown by the line 20. Thesmall portions of concrete discharged onto the main batch by theindividual vanes slide by gravity toward the forward end 4a of the drumand are again picked up by the vanes and moved toward the discharge endof the drum. The batch, in addition to being slightly higher at thedischarge end of the drum than at the opposite end, is also higher atthe far side of the drum than at the near side, as viewed in Figure 3,due to the direction of rotation of the drum. This also causes the smallportions of concrete It will be seen that the lines of juncture 5;:

picked up by the individual vanes to move transversely of the drum,thereby causing added'mixing thereof. The concrete below the line 20a ofFigure 3 is shown in section, while that above this line is shown inelevation.

Referring now to the embodiment illustrated in Figures 7 and 8, a drum3B having the same construction as is shown in Figure 1 is provided witha charging opening 3| having a cover 32, the drum also being providedwith a discharge opening and cover therefor at its left-hand end, asviewedin Figure '7, this cover, however, not being shown. Vanes 33, 34,35 and 3e are secured to the inside of the drum as by welding. Thesevanes, like those described in connection with the other embodiment, arecurved or bent along their longitudinal axes so as to make themtrough-shaped in order that they may retain the concrete which is pickedup by them until such time as the vanes are raised above the main batchof concrete. Thereafter, the small portions of concrete so raised by theindividual vanes are discharged again into the main batch of concrete,at points spaced longitudinally of the drum from the points at whichthey were picked up, as previously described. In this embodiment theproximal edges 3? are welded to the inside of the drum. so as to form acontinuous though imperfect helix about the drum. The distal edges 38,however, are spaced from each other at their adjacent ends so as toleave spaces between the adjacent vanes corresponding to the spaces fshown in Figure 4. Referring to Figure 8, the proximal edges 3'! of thevanes 33 and 34, for example, are welded to the inside surface of thedrum so as to form a continuous line of juncture with the drum, and suchline of juncture forms a continuous although imperfect helix about theinside surface of the drum. The distal edges 38 of the vanes 33 and 34,for example, at their adjacent ends 39 and M are spaced apart, thusleaving spaces through which water and concrete may pass when the vanesare submerged in the batch.

In either embodiment, when water is admitted to the batch, the waterfinds its'way into the interstices between the stone or gravel orcrushed rock, as the case may be, and is distributed in a manner whichdepends upon the shape of the mixing drum. Upon initiation of rotationof the drum, the water continues to remain in the bottom of the drum aslong as there is free space between the stone not occupied by a mixtureof sand and cement. This assists in properly distributing the waterduring the first few rotations of the 'drum and it is desirable that during this period the water should be free to flow wherever it may findspace in the interstices of the stone. In the present invention thisflow of water is permitted due to the provision of spaces between theadjacent ends of the vanes. If the vanes formed a continuous helixhaving watertight connections between the adjacent vanes, the vaneswould lift the water with the mix, thus preventing the free fiow ofwater from one side of the drum to the other during the first part ofthe mixing operation.

In each of the embodiments shown, the mixing vanes are arranged so thatthere are spaces between the ends of adjacent vanes which allow thewater to wet the batch during the early stages of mixing and whichduring the later stages allow some of the batch to flow through thesespaces so as to increase the efficiency of the mixing action.

By arranging the mixing vanes in the form of an interrupted helix, I amenabled to use vanes of a very simple construction. The faces of thevanes are bent or curved into trough-shape so as to retain concretethereon as the vanes are raised to their highest position. The vanes maybe arranged to form an interrupted helix along their proximal edges, asin the embodiment shown in Figures 1 through 6, or they may be arrangedto form an interrupted helix along their distal edges, as in theembodiment shown in Figures 7 and 8. In either embodiment, spaces areprovided between the ends of adjacent vanes. By arranging the vanes asdescribed, they may be made out of sheet metal and bent in only onedirection, namely, about the longitudinal axis of the vane, whereas ifthe vanes formed an uninterrupted helix, they would have to be curved orbent about their transverse axes in addition. The disposition of thevanes in an interrupted helix, therefore, simplifies the manufacture ofthe vanes and also increases the efficiency of the mixing action due tothe provision of spaces between theends of adjacent vanes.

I have illustrated and described two embodiments of my invention. It isto be understood, however, that the invention may be otherwise embodiedwithin the scope of the following claims. I

I claim:

.1. A truck mixer comprising a normally closed rotary drum with aremovable closure and hav-- ing lifting vanes curved in cross-sectionand having one edge contacting with the drum and adapted to raiseportions of the concrete above the level of the main batch and dischargethem onto the batch at points which are displaced longitudinally of thedrum from the points at which they were picked up by the vanes, saidvanes forming an interrupted helix about the drum at their proximaledges, the distal edges of adjacent vanes being connected togetheradjacent their ends so as to form a continuous though imperfect helixabout the drum, the vanes being so inclined with respect to thelongitudinal axis of the drum and, so shaped as to retain portions ofconcrete thereon when they are lifted above the level of the main batch.

2. A truck mixer comprising a normally closed rotary drum with aremovable closure and having lifting vanes curved in cross-section andhaving one edge contacting with the drum and adapted to raise portionsof the concrete above the level of the main batch and discharge themonto the batch at points which are displaced longitudinally of the drumfrom the points at which they were picked up by the vanes forming aninterrupted helix about the drum at their proximal edges and providingspaces between adjacent vanes, the. distal edges of adjacent vanes beingconnected together adjacent their ends so as to form a continuous thoughimperfect helix about the drum, said vanes being so inclined withrespect to the longitudinal axis of the drum and so shaped as to retainportions of concrete thereon when they are lifted above the level of themain batch.

3. A truck mixer comprising a normally closed rotary drum having itslength greater than its diameter, said drum being provided with aremovable closure, and having lifting vanes curved in cross-section andhaving one edge contacting with the drum and adapted to raise portionsof the concrete above the level of the main batch and discharge themonto the batch at points which are displaced longitudinally of the drumfrom the points at which they were picked up by the vanes, said vanesforming an interrupted helix about the drum at their proximal edges andproviding spaces between adjacent vanes, the distal edges of adjacentvanes being connected together adjacent their ends so as to form acontinuous though imperfect helix about the drum, said vanes being soinclined with respect to the longitudinal axis of the drum so shaped asto retain portions of concrete thereon when they are lifted above thelevel of the main batch.

4. A truck mixer comprising a normally closed rotary drum with aremovable closure and having lifting vanes curved in cross-section andhaving one edge contacting with the drum and adapted to raise portionsof the concrete above the level of the main batch and discharge themonto the batch at points which are displaced longitudinally of the drumfrom the points at which they were picked up by the vanes, said vanesforming an interrupted helix about the drum at their distal edges andproviding spaces between adjacent vanes, the proximal edges of adjacentvanes being connected together adjacent their ends so as to form acontinuous though imperfect helix about the drum, said vanes being soinclined with respect to the longitudinal axis of the drum and so shapedas to retain portions of concrete thereon when the vanes are liftedabove the level of the main batch.

5. A truck mixer comprising a normally closed rotary drum having itslength greater than its diameter, said drum being provided with aremovable closure, and having lifting vanes curved in cross-section andhaving one edge contacting with the drum and adapted to raise portionsof the concrete above the level of the main batch and discharge themonto the batch at points which are displaced longitudinally of the drumfrom the points at which they were picked up by the vanes, said vanesforming an interrupted helix about the drum at their distal edges andproviding spaces between adjacent vanes, the proximal edges of adjacentvanes being connected together adjacent their ends so as to form acontinuous though imperfect helix about the drum, said vanes being soinclined with respect to the longitudinal axis of the drum and so shapedas to retain portions of concrete thereon when the vanes are liftedabove the level of the main batch.

6. A truck mixer comprising a normally closed rotary drum with aremovable closure and having lifting vanes curved in cross-section andhaving one edge contacting with the drum and adapted to raise portionsof the concrete above the level of the main batch and discharge themonto the batch at points which are displaced longitudinally of the drumfrom the points at which they were picked up by the vanes, said vanesforming an interrupted helix about the drum at their proximal edges andproviding spaces between adjacent vanes, the distal edges of adjacentvanes being connected together adjacent their ends so as to form acontinuous though imperfect helix about the drum, said vanes beingtrough-shaped and so inclined with respect to the longitudinal axis ofthe drum as to retain portions of concrete thereon when the vanes arelifted above the level of the main batch, said vanes when in theiruppermost positions having their edges downwardly inclinedlongitudinally of the drum at an angle with the axis of the drumapproximately equal to the angle of repose of the concrete.

'7. A truck mixer comprising a normally closed rotary drum with aremovable closure and having lifting vanes curved in cross-section andhaving one edge contacting with the drum and adapted to raise portionsof the concrete above the level of the main batch and discharge themonto the batch at points which are displaced longitudinally of the drumfrom the points at Which they were picked up by the vanes, said vanesforming an interrupted helix about the L drum at their proximal edgesand providing spaces between adjacent vanes, the distal edges vofadjacent vanes being connected together adjacent their ends so as toform a continuous though imperfect helix about the drum, each of saidvanes being made out of a fiat plate bent only about its longitudinalaxis and not about its transverse axis, each vane being trough-shapedand so inclined with respect to the longitudinal axis of the drum as toretain a portion of concrete thereon when it is lifted above the levelof the main batch.

WILLIAM MAYO VENABLE.

